This invention relates to the field of track width control in readback elements such as magnetoresistive, giant magnetoresistive and spin tunneling heads.
Increasing areal density of magnetic storage media requires that the magnetic recording and reading heads be able to operate at ever-decreasing track widths. The width of the recorded track is determined, among other parameters, by the width of the write pole of the write head and the flying height of the write head. The size and geometry of the shields and leads also play a role in determining the recorded track width.
The prior art teaches that a write pole of the write head can be micro-machined to create a narrower write pole tip. The narrower write pole tip enables one to record magnetic domains, which represent information, in narrower tracks. In addition, it is known that to utilize the narrower tracks the erase-band width of the recording head must also be reduced. The erase-bands are the regions on both sides of the track where the field generated by the write pole is not sufficiently strong to write, but strong enough to erase previously recorded information. The prior art teaches trimming or otherwise altering the shape of the top pole of the write head to reduce the size of this erase-band. For example, Yimin Guo et al. in xe2x80x9cLow Fringe-Field and Narrow-Track MR Headsxe2x80x9d, IEEE Transactions on Magnetics, Vol. 33, No. 5, September 1997, pp. 2827-9 teach a focused ion beam (FIB) technique to pattern MR heads into different geometry at track edges to reduce the erase-band width. This is done in an integrated read/write head in which the shared pole is trimmed to minimize the side-erase field.
In order to take advantage of the narrower write track width and reduced side-erase fields, it is imperative that the read track width of the readback element or read head be reduced as well. The most popular types of read elements include magnetoresistive (MR) elements, giant magnetoresistive (GMR) elements and spin tunneling elements. At present, MR heads are typically made by photolithographically defining the active portion of the head. Unfortunately, due to practical limitations of the lithographic method, such as the diffraction limit of light, it is not economical to produce read heads much narrower than 500 nm. Meanwhile, MR head technology is already pushing present photolithographic techniques to their limits and these present methods will not be able to accommodate the next generation of MR heads.
The focused ion beam techniques for trimming write heads are described, e.g., by G. J. Athas et al. xe2x80x9cFocused Ion Beam System for Automated MEMS Prototyping and Processingxe2x80x9d, Proc. SPIExe2x80x94Int. Soc. Opt. Eng. (USA), Vol. 3223, 1997, pp. 198-207. Athas et al. suggest that the use of FIB techniques can be extended to milling the write pole and part of the upper shield of an integrated MR read head and inductive write head to reduce the MR head""s track width. Further details describing how the track width of an MR head and the off-track response are affected by the shield width are described by Charles Partee et al., xe2x80x9cOff-Track Response Versus Shield Width at the ABS for MR Headsxe2x80x9d, IEEE Transactions on Magnetics (USA), Vol. 33, No. 5, Pt. 1, September 1997, pp. 2887-9. Partee et al. employ FIB etching from the air bearing surface (ABS) of the slider in which the integrated head is mounted, to recess the shields by over 1 xcexcm to optimize track performance.
The MR head itself is not FIB machined in the prior art. That is because electrostatic discharge (ESD) damage to the MR head can occur, as pointed out by Partee et al. (supra). In fact, the magnetic material of MR heads is very sensitive and the application of FIB directly to MR head for narrowing its pole tip would burn out the MR head. This would result in either an inoperable head or a head that is magnetically noisy.
In view of the state of the art, it would be desirable to provide an MR head or other readback element whose track widths can be adjusted directly. Furthermore, it would be an advance over the prior art if the width of the read pole tip of such read head could be processed without negatively impacting the performance of the read head.
Accordingly, it is a primary object of the present invention to provide a readback element such as an MR head, a GMR head or a spin tunneling head in which the track width can be directly adjusted. Specifically, the effective track width of the read head is determined by the width of an active region of the pole tip.
It is another object of the invention to provide readback elements in which the tip portion adjustment is straightforward to implement at any point in the manufacturing process. In particular, the active region of the tip portion can be defined in a finished element.
The above objects and advantages, as well as numerous improvements attained by the readback element and method for making it are pointed out below.
The objects and advantages of the invention are achieved by a readback element for reading magnetic domains recorded in a magnetic storage medium. The readback element can be a magnetoresistive (MR), a giant magnetoresistive (GMR) or a spin tunnel element. It is made of a magnetically active material having a magnetic sensitivity. The element has a tip portion with a surface for facing the magnetic medium. The tip portion has an active region of width W made up of the magnetically active material. The active region is bounded by an inactive region in which the magnetically active material is deactivated such that the inactive region has no or almost no magnetic sensitivity. Width W of the active region of the tip portion is preferably less than 100 nm.
The inactive region can be a region implanted with ions which render the active material inactive. For example, the inactive region can be implanted with gallium, chromium, helium, neon, xenon, hydrogen, oxygen, nitrogen or other suitable ions. This can be achieved by focused ion beam (FIB) implantation or other suitable implanting method. Alternatively, the inactive regions in the tip portion can be formed by selectively removing the active material. Removal of the active material in the regions to be deactivated can be performed by FIB removal, etching or any other suitable technique.
Readback elements in accordance with the invention can be produced separately or in a batch process. In fact, adjustment of width W of the active portion of the tip portion can be performed in a finished readback element.